A Photomicroscopic Study on the Growth Rates of Calcium Oxalate Crystals in a New Synthetic Urine without Inhibitors and with Various Inhibitors

A photomicroscopic growth apparatus was used to study the growth rates of calcium oxalate crystals in a new synthetic urine without inhibitors and with various inhibitors, including magnesium ions, citrate ions, chondroitin sulfate ions, and phytate ions. The dependence of growth rates on supersaturation at different temperatures without inhibitors was investigated using a power law model in terms of the Arrhenius form. The effects of various inhibitors on the growth rates of calcium oxalate indicated that the inhibition of growth rates increases in the order magnesium ions < citrate ions < chondroitin sulfate ions < phytate ions. The polymorphic forms of calcium oxalate crystals without inhibitors and with various inhibitors were examined by scanning electron microscopy.

Synthesis of Silicon- and Carbonate-doped Biomimetic Hydroxyapatite in the Presence of Citrate Ions and its Physicochemical, Bioactivity Properties

The present study investigated the phase composition, the structural, morphological, and bioactivity properties of silicon- and carbonate-doped biomimetic hydroxyapatite synthesized by precipitation from aqueous solutions in the presence of different amounts of citrate ions. The X-ray diffraction and Fourier transform infrared spectroscopy analyses confirmed that all the samples exhibited single-phase. Base on the results of the morphological study, all the obtained samples consisted of porous agglomerated particles made up of tiny crystallites in the nanometer range. The change in structural order, as well as the decrease in particle size and degree of crystallinity result from the presence of citrate ions were revealed by X-ray diffraction, dynamic light scattering, and scanning electron microscopy analyses. Bioactivity properties of samples were studied by analyzing their bioresorbability in physiological saline (ω (NaCl) = 0.9%) and evaluating their solubility in SBF solution after a certain period of soaking time. The amount of the released Ca2+ ions was found to increase with the increasing concentration of citrate ions introduced in the synthesis process. The better solubility of material with the presence of citrate ions was beneficial in the growth of apatite on its surface that made produced material more biocompatible.

SYNTHESIS AND INVESTIGATION OF BIOMIMETIC HYDROXYAPATITES DOPED BY SILICATE AND CARBONATE ANIONS IN THE PRESENCE OF CITRATE IONS

In the present work, biomimetic hydroxyapatite (BHAP) doped with silicate and carbonate anions in the presence of citrate ions are synthesized by chemical precipitation from aqueous solutions. According to the results of X-ray phase analysis (XRD), all the obtained materials are single-phase. Scanning electron microscopy (SEM) demonstrates that BHAP powders are a collection of agglomerated particles with similar morphology. Dynamic light scattering confirms that the synthesized BHAPs consist of agglomerates 1–4μm in size. For all samples, with an increase in the number of introduced citrate ions, decreases in the average crystallite size and degree of crystallinity are observed. With an increase in the concentration of citrate ions, the content of agglomerate fractions of 1–2μm in size increases from 70.16 to 75.43%. The solubility of hydroxyapatite samples in physiological saline (ω(NaCl) = 0.9%) at temperatures of 22°C and 37°C is studied. It is revealed that for all synthesized BHAPs, the amount of released Ca2+ ions into the liquid phase increases. The maximum yield of Ca2+ ions in physiological saline is recorded in BHAP with the highest content of citrate ions. The obtained results allow to consider the synthesized BHAP as a promising medical biomaterial for the regeneration of bone tissue.

Dynamics of Binding of Lysozyme with Gold Nanoparticles: Corona Formation and its Correlation with a Naked-Eye-Based Colorimetric Approach

The interaction between colloidal gold nanoparticles (AuNPs) and lysozyme (Lyz) has been studied through spectroscopic and microscopic measurements, molecular docking simulation and colorimetric measurements to investigate corona formation and the mechanism, affinity, number of sites and stoichiometry of binding. Molecular docking simulation endorses that, at physiological pH, the interaction between basic NH2 group of arginine and citrate ions is predominant than the interaction between citrate ions and the positive surface charge of the bare AuNPs that result in the desorption of citrate ions from Au surfaces and finally, electrostatic interaction between [Formula: see text] group of arginine and positive charge surface of AuNPs results in the adsorption of Lyz on Au surfaces. As observed from Benesi–Hildebrand and fluorescence analyses, the ground state complex formation between Lyz and AuNPs requires several minutes, which is approximately 11 min in the present work to attain stoichiometric ratio 1:1. CD spectra indicate insignificant or no conformational change in the secondary structure of Lyz in the presence of AuNPs. The time variation of LSPR peak position and peak height in the presence of Lyz have been studied extensively through spectroscopic and microscopic measurements. Detailed discussion on the probable time-specific roles of change in local dielectric constant, plasmon coupling and electrostatic interaction on these variations has been presented. Colorimetric change of the AuNPs-Lyz system with time has been analyzed by measuring the red, blue and green color fractions as well as its correlation with the process of corona formation and aggregation has been investigated to propose a novel naked eye colorimetric approach of studying these processes in AuNPs-Lyz system.

Cooperative effects of Na+ and citrates on the dissolution of calcium oxalate crystals

Cooperative role of sodium and citrate ions in the dissolution of calcium oxalate crystals.